Connecting to SAP (SRM) thru XI

I am trying to gather as much information as possible to make a recommendation of using XI for transporting multiple (large) files into SAP SRM mainly. There is also the possibility of getting back some data from SRM.

We are looking for the best solution that would help us achieve this - probably make RFC calls and get back Idocs (using JCo if you have to) or using SOAP to access the information/data from SAP MDM / SRM

Thanks,

Bala